File:Kimberlite (Premier Kimberlite Pipe, Mesoproterozoic, ~1.2 Ga; Premier Mine, near Cullinan, northeastern South Africa).jpg
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[edit]DescriptionKimberlite (Premier Kimberlite Pipe, Mesoproterozoic, ~1.2 Ga; Premier Mine, near Cullinan, northeastern South Africa).jpg |
English: Premier Kimberlite from the Mesoproterozoic of South Africa (4.5 centimeters across at its widest).
Kimberlites and lamproites have tremendous economic importance because they are host rocks for gem-grade and industrial-grade diamonds. Kimberlites & lamproites are unusual igneous bodies having overall pipe-shaped geometries. Their mode of formation is only moderately understood because they have not been observed forming. Kimberlites & lamproites are known from scattered localities throughout the world - only some are significantly diamondiferous. Classic localities for diamonds are India and Brazil. Africa was also discovered to have many kimberlites and is world-famous for producing large numbers of diamonds. Other notable diamondiferous kimberlite-lamproite occurrences include Russia, China, northwestern Australia, and northwestern Canada. Kimberlites are named for the town of Kimberley, South Africa. Several kimberlite pipes occur in the Kimberley area. Kimberlites have a gently tapering-downward, pipe-shaped cross-section. Lamproites have a cross-section more closely resembling that of a martini glass. The rock shown above is from the Premier Kimberlite - the largest gem-quality diamond ever found came from this unit. The Premier Kimberlite Pipe is located near the town of Cullinan, ~30 km northeast of Pretoria, in northeastern South Africa. When found in 1905, the Cullinan Diamond measured 10.5 cm (4.25 inches) across at its widest (about the size of a fist), and weighed ~1.5 pounds. Uncut, the Cullinan was 3026 carats. The Cullinan was cut into 105 gemstones, the largest of which is the Great Star of Africa (530 carats), on display with the British Crown Jewels in the Tower of London. The Premier Kimberlite Pipe erupted about 1.2 billion years ago, during the Mesoproterozoic. It is significantly diamondiferous. Published inclusion dating studies have shown that Premier diamonds fall out into three age groups: 1) ~1.2 billion year eclogitic diamonds (Mesoproterozoic) 2) ~1.9 billion year lherzolitic diamonds (Paleoproterozoic) 3) ~3.2 billion year diamonds (Mesoarchean) |
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Source | https://www.flickr.com/photos/47445767@N05/14800332986/ |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14800332986. It was reviewed on 2 November 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
2 November 2020
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current | 17:02, 2 November 2020 | ![]() | 1,227 × 1,042 (1,000 KB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/14800332986/ with UploadWizard |
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Width | 1,227 px |
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Height | 1,042 px |
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Compression scheme | Uncompressed |
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Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 650 dpi |
Vertical resolution | 650 dpi |
Data arrangement | chunky format |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 23:35, 15 December 2006 |
Color space | Uncalibrated |
Image width | 1,227 px |
Image height | 1,042 px |
Date and time of digitizing | 18:35, 15 December 2006 |
Date metadata was last modified | 18:35, 15 December 2006 |